Tephrocactus aoracanthus

Habit and spine variation

The species grows in central-western Argentina on slopes, gravel and sand, at about 500–2500 m above sea level in the treatment studied. It may reach about 50 cm tall. Segments are ovoid or globose and separate easily at the constrictions. In the 2019 description, strong, straight spines were particularly developed on their upper parts. [Las Peñas et al. 2019]

Pale flowers develop into dry, dehiscent fruit. Sepal tips may be elongated into rigid points. Seeds have a corky covering of funicular origin. These traits accompany pronounced stem segmentation and a fibrous root system. [Las Peñas et al. 2019, appendix 1]

The former name paediophilus

POWO places the name Tephrocactus paediophilus in the synonymy of T. aoracanthus. The 2019 paper analysed the two identifications separately. Material described as T. paediophilus had long, twisted, grooved spines distributed over more of the segment surface. Data for these specimens retain their own historical identification in the profile. [2-WWW] [Las Peñas et al. 2019]

In T. aoracanthus as narrowly defined in that paper, 2n = 242 was counted, corresponding to 22 basic sets. Material described as T. paediophilus had 2n = 319, or 29 sets. These are two results concerning the specimens studied. The current merging of names does not establish one fixed number for the entire species. [Las Peñas et al. 2019, Table 2] [2-WWW]

A detached segment as a propagule

Almirón and coauthors studied segment connections in T. aoracanthus and transport of its fragments by rainfall runoff. A propagule, meaning a fragment capable of starting a new plant, may detach, move with water and come to rest in a depression. Separate experiments concerned breakage mechanics and the path of movement. [Almirón et al. 2016] [Almirón et al. 2019]

Stem fragmentation enables reproduction without a seed stage. The importance of this mechanism depends on the strength of segment connections and the chance of rooting after movement. Process stages and measurement conditions are developed in the article on clonal dispersal by rainwater. [Almirón et al. 2016] [Almirón et al. 2019]

Spines in a dusty environment

Near a cement factory, spine length, segment diameter and mass were compared at different distances and on two sides of the plant. Some differences depended jointly on distance and position. Moving plants from near the factory to a more distant site was associated with production of shorter spines. [Drack and Vázquez 2018]

A separate six-month experiment included 88 segments subjected to dust application to above-ground parts, dust addition to soil, both treatments or a control. No significant change in spine length or number was found. Some mass parameters did change. The results indicate plant plasticity and complex site effects, while field correlation alone does not establish a single cause of spine development. [Drack and Vázquez 2018]

Cultivation in archival material

The archival review of Tephrocactus cultivation describes dry dormancy at temperatures no higher than 10°C and propagation by rooting detached segments. The author notes that severe drying may increase segment shedding. The recommendations concern the group discussed, with no defined minimum temperature or separately determined rooting percentage for this species. The retained earlier archival profile includes references to pages in the material. [Kaktusy i Inne 2005c, p. pliku 2–4]